In wireless systems, a wireless station typically transmits a frame of voice signals at a nominal 8 kbps (i.e., 8 kbps to 13 kbps) rate. If a wireless system conforms with a particular protocol, e.g., the well-known IS-95 protocol, then such a frame may be received by more than one base station as illustrated in FIG. 1. A base station, e.g., base stations BS 2-1 and/or BS 2-2, that receives a frame of signals supplies the frame and an associated signal-to-noise ratio (SN/R) value to a so-called Mobile Switching Center (MSC), e.g., MSC 5. MSC 5, in turn, directs the received frame to a conventional Frame Selector (FS) circuit 3. Frame selector 3 then selects the frame of signals having the highest S/N R value and outputs that frame to a conventional voice coder (vocoder) circuit 4. Voice Coder (VC) 4 converts ("upcodes") the frame of nominal 8 kbps voice signals transmitted by the wireless station, e.g., wireless station 1, to 64 kbps PCM coded signals and outputs the converted frame of signals to network 6 for delivery to an intended destination 7 (assuming that the routing for the frame had already been established).
Disadvantageously, an MSC (as well as a so-called Mobile Terminal Switching Center (MTSO)) converts voice signals that it receives at a nominal 8 kbps rate from a base station to 64 kbps PCM irrespective of the type of network that will receive the converted signals directly from the MSC. Because of this, system bandwidth is not used efficiently. For example, if network 6 happens to be another MSC and destination 7 is another wireless terminal, then even in that instance MSC 5 converts the 8 kbps signals to 64 kbps for delivery to network 6. Network 6 then re-converts the 64 kbps signals that it receives from MSC 5 to a nominal 8 kbps for delivery to wireless destination 7. Such conversion and re-conversion is clearly unnecessary overhead. It also impairs the quality of the voice signals. As another example, assume as shown in FIG. 2 that the route to destination 7 includes packet switches 8 and 9, in which the latter switch output signals to network 6 for delivery to destination 7. Here too MSC 5 using VC 4 converts the nominal 8 kbps signals outputted by FS 3 to a 64 kbps rate and supplies the result to packet switch 8. Packet switch 8, in turn, forms the signals into a packet and in accordance with its routing table delivers the packet to switch 9, which then unloads the contents of the packet for forwarding to PSTN network 6. However, there is no need to convert the nominal 8 kbps signals to 64 kbps signals at MSC 5 since a packet switch can readily handle 8 kbps traffic.
Accordingly, such unnecessary conversion or the conversion of the nominal 8 kbps signals at the wrong point in the network leads to inefficient use of the system bandwidth.